SU736296A1 - Three-phase-m-phase direct frequency converter - Google Patents

Description

The invention relates to converter technology and can be used to power frequency-control ac electric drives in autonomous power sources with a variable speed of rotation of the generator drive shaft to obtain a stable frequency, as well as to power various electromagnetic devices operating on the principle of a traveling field, for example, for powering linear motors or electromagnetic stirring installations for liquid metals. Direct frequency converters with natural switching thyristors-NFC with EC 1 are known. Their drawbacks are the difficulty of obtaining a high-quality output voltage, as well as a low input power factor. Direct frequency converters with art-switching thyristors-NFC with IR are also known, which allow eliminate these disadvantages 2, 3, 4 and 5. The most effective algorithm for controlling such converters is the so-called cyclic connection algorithm at regular intervals s time network load phases. The frequency of the main harmonic of the output voltage is equal to f - f - f - 1 - 1 T, T, t, T2, where f is the frequency of the power supply voltage; f is the frequency of connection to the load of the same phase of the power supply network. A feature of converters that implement such an algorithm is to build them on fully controllable keys with two-way conductivity (otherwise on AC keys). With higher demands on the quality consumed by the current transducer and the output voltage, the known solutions become unacceptable. The smallest harmonic ratio of the output voltage provided by transformer-thyristor converters and converters made in a bridge circuit with an equivalent number of phases 6 (participating in the formation of the output voltage) is 0.31. With real active-inductive

When loaded, the input current harmonics also approach this value.

Converters of this type provide the output voltage at the common point less than the supply voltage. In the overwhelming number of applications, this requires the installation of a matching transformer at the input of the converter. In cases where the use of a matching transformer is unavoidable, it is advisable to use it not only for coordination purposes, but also for other purposes, for example, for organizing a different converter structure, providing more high quality current consumption and output voltage. This idea is implemented in the proposed solution. The closest in technical essence and the achieved result to the invention is a converter with a three-phase transformer with a primary and main secondary winding complexes and three-phase bridges on controlled keys with two-sided conductivity, with inputs. These bridges are connected to the ends of the windings of the TACs of the set, and the output pins are formed by the output. 5 three-phase bridges 5}. A disadvantage of the known converter is the low quality of output voltage and input current for a number of knockouts (for example, for moving objects), which requires the use of filters, degrading power and maso- gaba-. piiTHtae indicators, as well as creating a specific application case and some additional problems, for example, dry transients; generator regeneration and t,,

The aim of the invention is to improve the quality of the output and input currents,

This is achieved by the fact that a known converter containing a matching three-phase transformer with primary and main secondary sets of rehafenny windings and three-phase hectares of bridges on controlled cells: two-sided conductors, inputs connected to the ends of the windings of the main secondary set, and outputs forming output terminals {converters ), is supplied with an additional: ityelny set of secondary windings of the transformer and two additional valve b1 b1 with control keys on their outputs, and the windings in of the main core set were filled with taps connected to the same ends of the three-phase winding of the additional secondary set according to the zigzag scheme, while the opposite and opposite to each other ends of the three-phase windings of the secondary main and additional sets are connected to the input terminals of the additional valve bridges.

FIG. 1 is a schematic diagram of the proposed converter, in FIG. 2 shows a modification of the converter in Fig. 1. In Fig. 3, vector diagrams explaining the principle of forming the output voltage; in fig. 4 shows timing diagrams of the output voltage and the key switching algorithm of the converter in FIG. 5 is a control system diagram for controlling the input voltages and frequency of the converter; FIG. 6 shows timing diagrams explaining the operation of the control system.

The converter contains a three-phase transformer (x has a transformer 1 with a primary set of 2 and with a primary 3 and an additional 4 secondary sets of three-phase windings, and the windings of the main secondary kit are provided with taps 5-7, as well as three-phase bridges with controlled two-sided conductivity ( for example, bridge 8 on keys 11–16) to two valve bridges 17 and 18 with controllable key elements 19 and 20 on their outlets.The output terminals 21–26 of the converter are formed by the outputs of bridges 8–10, and the number of these bridges is equal to the number of output ph of the transducer (in this case).

In some cases, it may be more appropriate to modify the converter shown in FIG. 2, the difference of this solution lies only in the fact that the additional set of three-phase windings is performed on the primary (and not on the secondary side) and the winding of the primary set (and non-secondary) are made with tap-offs. In this case, at certain ratios of the supply mains voltage and the load, the valve MociM 17 and 18, taking into account the output flush valve range, will have better overall dimensions.

The principle of forming the output voltage of the converter is illustrated in FIGS. 3 and 4.

Claims (3)

The essence of the formation of the output voltage is that two three-phase systems (nd voltage, (see, Fig. 3, Fig. 3, c)) are shifted between themselves by angles / b Switching the keys of bridges 8–10 accordingly, each of the bridges can receive any of the six-phase cHCTefvftj voltages (see fig.3, b) from one, three-phase voltage system of 1 cm 3, a) and any of the voltages of another six-phase system (see fig, 3, d) from another cHCTevH of voltages (see fig, 3, c). An alternate connection at equal intervals of time, then one, then another three-phase system of voltages to the inputs of bridges 8-10, allows to output any of the voltages of the twelve-phase system of voltages (see Fig. 15), t. e. Thus, to obtain the equivalent phase phase of the 1P power supply network, s, equal to 12. In this case, the closure of the key 19 ensures that the voltages shown in FIG. 3, a, and the closure of the key 20 (and, accordingly, the opening of the key 19) supply to the same inputs of the voltage system (see FIG. 3 of the memory c). To be specific, consider a few switching points. The designation of the voltage vectors in FIG. 3, d corresponds to the designations of the phases a, b, c of the secondary windings of the transformer in FIG. In FIG. 3, d, and also in FIG. 4, and the voltage of the twelve-phase system of voltages is indicated by numbers in quotation marks (to simplify the notation in Fig. 4, a). The key switching algorithms 19 and 20% og as well the key switching algorithms 11-16 of one bridge 8 are shown in FIG. 4, b. In the interval, according to the diagrams in FIG. 4, the keys 19, 11 and 14 are turned on, Phase output voltage (i.e., asv) is supplied to the output terminals 21 and 22 of the converter. At time t, keys 20, 12, and 1 are closed, and keys 19, 11, and 14 are opened. Output pins 21, 22 are supplied with a voltage of phase 2 (i.e., sa), using the timing diagrams in FIG. 4, it is easy to follow the process of forming the output voltage on the entire segment T2 / 2. The non-shaded part of the key switching algorithm in FIG. 4, 6 corresponds to the direction of the current (with a clear load), indicated by a solid arrow. The part of the algorithms marked by shading corresponds to the opposite direction of the Current through the keys (shown in paragraph). As applied to the thyristor execution of the keys, for example, in the form of counter-parallelly connected thyristors, this means that only thyristors work at moments not marked by shading. marked with shading are other thyristors of the same key. In this case, to determine the thyristor, which must be included, information on the direction of the current in the load is used. The voltages of the ocTa.nbFiijx phases are similarly formed. Mn-lo output phase m in such a converter can be implemented by any. Most of all, just implement the cases with m 2, 3, 4p b. The quality of the output voltage and input current in the proposed converter, measured by the harmonic coefficient, is twice as good as in the known similar solutions (0., 152 vs. 0.31). Combinations of semiconductor elements described in, for example, 5 can be used as controllable keys with two-sided conductivity. The number of turns of the windings of the additional secondary (or primary in D.2) sets of 4 is less than the number of turns of the windings of the main secondary (or primary in Fig. 2) of the set 3 and is equal to part of the number of turns of the windings of the primary secondary set from the beginning of these windings to taps. The converter has all the advantages inherent in direct frequency converters with a cyclic control algorithm. In the considered variants of converters, the windings of the main and additional sets are organized in the most rational way from the point of view of the mass-dimensional parameters of the transformer. In principle, it is possible to use two additional sets of windings (and not one) and one main set of windings without taps. However, this leads to increased masses of copper windings and, accordingly, steel transformer magnetic circuit. The use of more efficient autotransformer (and not transformer) communications, i.e. The combination of the windings of one additional set with the windings of the main set eliminates this disadvantage. In addition, such windings also reduce the magnitude of surges - bursts that can occur when switching keys (19 and 20) due to the leakage inductances of the windings. The reverse voltages applied to the diodes of bridges (17 and 18) to keys 19 and 20 and to keys of bridges 8-10 are 1.27 and 8-.0 245 respectively and ,, ° where and, „is the effective value on the yarn winding phase of the main set. In an embodiment of a transformer with two additional sets of windings, i.e. when using a transformer, rather than an autotransformer connection between the battens of the corresponding sets, changing the polarity of the connection of the windings of the wasps by 180; Ovnogo and additional sets, you can halve the number of switches key bridges 8-10. However, this significantly increases the reverse voltage on the 17-20 Vao.SU.j elements. This means an increase in 3.69 p of the rated power of the elements 17-20 in comparison with the winding arrangement (see fig, 1 and 2). When choosing a variant in a particular case of application, this circumstance must be taken into account. The possibility of adjusting the magnitude of the output voltage is explained by the time diagrams in Fig. 6 and the control system diagram in Fig. 5. Switching algorithms for keys I-16 of the same phase and keys 19 and are shown in FIG. 6.6. Regulation is provided by introducing a variable pause t between switches of keys 19 and 20. To pass reactive current at these moments, keys of one bridge stand, for example keys 11 and 12, are shown, as shown in FIG. 6.6. The formation of the necessary pulse sequences for controlling the keys 11-16 and 19 and 20 is provided by the control system, as shown in FIG. 5. It contains a master oscillator 27, a pulse width modulator 28, a twelve-stroke pulse distributor 29, an input connected to the MH output (25) of the generator 27 through the first divider hour 30, made in the form of a trigger with a counting input, and a logical node 31, the outputs connected to the correcting inputs of the corresponding keys via the decoupling and amplification unit 32, and the second frequency divider 3 also made in the form of a trigger with counting input 28 can be executed — for example, in the form of a saw voltage generator 34 and comparator 35. Logic node 31 contains a logical element NOT 36, eight two-input logic elements AND (37-44) and six four-input logical elements OR (45-50). All interconnections between logic elements and control system nodes are shown in FIG. The main signals arriving at the inputs of the logic node 31 are shown in FIG. Th, -v At the same time, the output voltages of the nodes are denoted by the letter AND with the digital index corresponding to the number of these nodes;. The number of outputs of the generator 29 is taken from top to bottom. The key switching algorithm shown in Fig. 5b and the signals at the corresponding outputs of the logic node 31 have the same appearance. in the case of using the described solution for building an autonomous power supply system in the form of a generator with variable shaft speed and frequency converter, the need for a transformer is eliminated, and the core windings of the generator are performed in the same way as the secondary windings of the transformer. Regulation of the output voltage in this case can be ensured by appropriate regulation of the excitation of the generator. The most effective advantages of the converter can be realized at lower input and output frequencies (of the order of units and tens of Hz), for example, when converting the industrial frequency of 50 Hz to a lower or to a higher one. Invention Three-phase-to-phase direct frequency converter containing a matching three-phase transformer with primary and main secondary sets of three-phase windings and m three-phase bridges on controlled keys with double-sided conductivity, and the inputs of these bridges are connected to one of the ends of the windings of the main secondary set, the output pins are formed by the output pins of bridges, characterized in that, in order to improve the quality of the input and output currents, it is equipped with two additional ventilation bridges with controllable keys at their outputs and an additional set of transformer secondary windings, the windings of the main secondary kit being made with taps connected to one of the ends of the three-phase winding of the additional secondary complex, zigzag opposite and opposite to each other of the three-phase windings of the secondary primary and secondary sets are connected to the input terminals of additional valve bridges, the sources of information taken into account when Expertise 1, Daniushevska E.Yu. Thyristor converters in DC and AC controlled electric drive systems, - Sb. Automated electric drive of industrial mechanisms, vol. 3, ML, Energie, 1966, Co 271-272, 2, Swiss Patent 47-6419, cl. H 02 p 7/62, H 02 p 13/30,. 3. Japanese patent 48-31408, cl. 56 B 3, 1973. 4, Electricity No. I, 1977, p. 62-67. 5. Sat. Modern tasks of converting equipment, Issue 2, Kiev, Institute of Electrodynamics, Academy of Sciences of the Ukrainian SSR, 1975, p. 132-140 (prototype). 13 15 g e acSa Sa CO vaas FIG. KW to 19 to 20 f.S. t t M M M I I I I I I I I I I I I M L j uch f A A / V UCH / 4 / U  r-l r-ij-i-c rn n n rj and ie Up ,, Upuz pui U. pus  Up.n / R / y, # Z ai J j 7 7 7 li 3 Ti